To form line structures with 80 µm hills and valleys width into a Si <100> substrate, thermal oxidation, lithography, and wet chemical etching steps were necessary. During the procedure a inclination was formed in the transition zone between the hills and valleys, due to the KOH etching of the Si <100> substrate. A valley depth of 3.4 µm was measured after the KOH etching. To enable a self-propagating reaction on the structured Si surface, as seen in the video, a 1.2 µm thick layer of thermal SiO2 was produced. The 5 µm thick Al/Ni multilayers were then deposited with direct current magnetron sputtering in an atomic ratio of 1:1, while keeping a bilayer thickness of 50 nm. During the deposition, defects in the multilayers located at the inclined area between the hills and valleys were formed. As shown in the publication of Jaekel et al. (2022) the defects are gaps at the inclined transition zone [1]. During the ignition of the sample, these defects prevented a reaction of the multilayers deposited on the hills. Therefore, a new potential way to guide the reaction on a specific pathway could be established. The video displays an example of a self-propagating reaction, in which the bright reaction front propagates only in the valleys, with an average velocity of 7.4 m/s. The velocity is calculated with the pixels size of 34.4827 µm and the frame rate of 50000 per second. Highspeed-camera FASTCAM SA-X2 type 480K-M3 was used to obtain the video in a resolution of 512x408 pixels.

{"references": ["K. Jaekel, H. Bartsch, J. M\u00fcller, Y. H. S. Camposano, S. Matthes and P. Schaaf, \"Effect of line structures on the self-propagating reaction of Al/Ni multilayer,\" 2022 IEEE 9th Electronics System-Integration Technology Conference (ESTC), Sibiu, Romania, 2022, pp. 379-382, doi: 10.1109/ESTC55720.2022.9939472"]}

Funding: The Deutsche Forschungsgemeinschaft (DFG) supported this study by granting BA 6161/1-1 and BE3198/7-1.